Deformable Exchanger

ABSTRACT

A heat exchanger includes two mutually isolated fluid circuits in close thermal contact, a first fluid circuit, or bundle ( 3 ), consisting of a helical winding of two walls and the second circuit consisting of a chamber containing the bundle ( 3 ), each circuit including its own fluid input and output elements. The heat exchanger is characterized in that the bundle is elastically deformable under the effect of excess pressure or low pressure.

The present invention relates to exchangers and notably to exchangersfor providing heat exchange between two fluids.

Generally, it is known that heat exchangers applying fluids consist oftwo mutually isolated circuits but which are in thermal contact as closeas possible, and through which travel both fluids respectively.

It is also known that maintenance of the heat exchangers and inparticular their cleaning, is generally a long operation, difficult toperform efficiently or even sometimes impossible. Finally it is knownthat such cleaning sometimes consists of removing for example scalewhich was deposited in the exchanger along with the use of the latter.

Exchangers of the so-called plate and gasket type formed from more metalsheets may be disassembled plate by plate, so that it is therebypossible to access their circuits, even if this is a long operation toimplement. However, these exchangers, because of their actual design,are therefore costly to utilize.

Moreover exchangers of the brazed plate type cannot be disassembled andtherefore their circuits are also difficult to clean.

This is why focus was on helical exchangers which are made from twometal sheets which are wound and maintained spaced apart from each otherby pins. After winding them, one proceeds with welding of the metalsheet edges in order to generate two independent fluid circuits, i.e. afirst circuit comprised between both wound and welded metal sheets and asecond circuit comprised between the different turns of the winding. Forreasons related to the construction method, the user does not haveaccess both to the space between both wound sheets and to the onebetween the various turns of the winding, so that it is impossible toachieve efficient mechanical cleaning of this exchanger and that onemust content oneself with chemical type cleaning, which is ofteninsufficient for certain applications.

Now these exchangers, because of their constitution, require that forproper effective maintenance, access be provided not only to the actualwinding but also to their spaces between the turns. Now these are allthe more reduced which makes cleaning of the exchangers even moreproblematic especially when dealing with removal of deposits such asscale from the latter.

However, a certain number of applications which would be open to thistype of exchangers, such as uses in the food industry field, the medicalfield, the pharmaceutical field and in fine chemistry, or notably inelectronics, involve periodical cleanings with high efficiency.

The object of the present invention is to propose means with which auser may carry out such cleaning and this in a simple and fast way.

Thus, the object of the invention is a heat exchanger comprising twomutually isolated fluid circuits in intimate thermal exchange contact, afirst fluid circuit or bundle, being formed by a helical winding of twowalls and the second circuit being formed by an chamber containing thebundle, each circuit including its own fluid input and output means,characterized in that the bundle is elastically deformable under theeffect of excess pressure or low pressure.

According to the invention, the chamber will preferentially be of atubular shape and, when the internal pressure of the bundle will beequal to its external pressure, its outer diameter will be slightly lessthan or equal to the inner diameter of the chamber. The diameterdifference between the inner face of the chamber and the outer face ofthe bundle will be less than 6% of the diameter of the latter.

The tubular casing may include two bottoms, at least one of which may beremovable, these bottoms being respectively crossed by the fluid inputand output means, and means capable of providing the seal between thebottoms and the fluid input and output means of the bundle. These inputand output means may respectively consist of two longitudinal tubes andthe means capable of providing the seal between the tubes and thebottoms may consist of O-ring gaskets or a stuffing box.

The object of the present invention is also a method for intervening,such as for example for cleaning, on a bundle of a helical typeexchanger including two mutually isolated fluid circuits in intimatethermal exchange contact, a first fluid circuit, or bundle, being formedby a helical winding of two walls, or bundle, and the second circuitbeing formed by a space delimited by a casing containing the bundle,each circuit including its own fluid input or output means,characterized in that it includes the steps of:

submitting before its removal, the bundle to low pressure, and/or tocooling relatively to its casing, so as to cause it to contract,

once the bundle is extracted from its casing, interrupting the lowpressure,

proceeding with intervention on the bundle,

again submitting the bundle to low pressure and/or to cooling relativelyto its casing, so as to cause it to contract before it being placed inthe casing,

setting the bundle back to pressure and/or to room temperature as soonas it has been placed back in its casing.

According to the invention, the bundle may be made so that it isdeformable under the effect of a pressure difference between the bundleand the chamber, of excess pressure or low pressure and it may beprovided with an outer diameter less than the inner diameter of thecasing, and periodical excess pressures and/or low pressures may beapplied to the bundle in order to change its outer diameter and breakthe brittle components which may have adhered to the walls (scale) whichare deposited on it.

The method may include a preliminary step consisting of disconnectingthe bundle from its circuit.

It is also possible according to the invention to promote theintervention operation by submitting the bundle, once the latter isextracted from its casing, and before the intervention, to excesspressure and/or to heating relatively to the casing, which will have theeffect of spacing out the turns of the winding from each other.

In order to avoid submitting the bundle to too strong pressure with theconsequences of deforming the metal forming the winding beyond itselastic limit, a limiter, the diameter of which will be equal to themaximum diameter which should not be exceeded as desired, will bepositioned around the bundle. This limiter may consist of a ring orsheath.

An embodiment of the present invention will be described hereafter as anon-limiting example, with reference to the appended drawing wherein:

FIG. 1 is a schematic cross-sectional view of an exchanger according tothe invention.

FIG. 2 is a perspective view of a bundle forming the exchangerillustrated in FIG. 1.

FIG. 3 is a perspective view of the casing containing the bundleillustrated in FIG. 2.

FIGS. 4 and 5 are perspective views of a bundle of an exchangeraccording to the invention, respectively fitted with a sleeve and ringsfor limiting its outer diameter.

An exchanger according to the invention which essentially consists of acasing 1 which is intended to receive a bundle 3, is illustrated inFIGS. 1-3.

The bundle 3 consists of a helical winding of two metal sheets 5 whichare spaced apart from each other and welded so as to provide betweenthem a fluid circuit. Spacing out these two metal sheets 5 is providedby a series of “pins” 7 which are generated and distributed over thesurface of the metal sheets before folding the latter. These pins 7,once the winding has been carried out, also provide regular andcontrolled spacing between the turns. The space between both foldedmetal sheets includes a supply conduit 9 and a discharge conduit 11.

The casing 1 consists of a cylindrical tube 13, the inner diameter ofwhich corresponds to the outer diameter of the bundle 3, so as to beable to receive the latter. The casing 1, as illustrated in FIG. 3, hasa fluid supply conduit 15 and a discharge conduit 17. The tube 13 isclosed by a bottom 19 which is fixed and which is crossed by thedischarge conduit 11 of the bundle 3 with interposition of a O-ring sealgasket 23 on the one hand and at its other end, by a removable bottom25, and which for this purpose is maintained by clamping brackets 27which bear upon a flange 29 of the tube 13, on the other hand. An O-ringgasket 31 provides the seal between the lid 25 and the supply conduit 9of the bundle 3.

Thus, by simply disassembling the removable bottom 25, access isprovided to the bundle 3, after having either disconnected the latterfrom the supply pipes connected to its conduits 9 and 11, or bypositioning an outlet 11 with sufficient length.

It is known that this type of exchangers requires minimum play betweenthe bundle 3 and the inner face of the tube in which it is positioned.Now, in certain exchangers, notably in stainless steel, which areintended for applications which require particular attention, notably inthe field of pharmacy or in the food industry field, it is required thatthe bundle be able to be removed from its casing without formingscratches on the inner wall of the tube during this operation, suchscratches notably forming nesting locations for bacteria.

In order to solve this problem, the bundle 3 is caused to be deformableat its diameter under the effect of a stress. In order to thereby makethe bundle deformable, the thickness and the nature of the steel usedwill be varied.

On an assembled exchanger intended to be disassembled, retraction of thebundle 3 will be caused by connecting one of the inlets 9 or 11 to thelatter, to a vacuum pump, after having blocked the other inlet, in orderto create partial vacuum. The bundle may then be disassembled withoutany risk of scratching the inner face of the casing 1. Once the bundle 3has been disassembled, the vacuum will be suppressed so that it willexpand and resume its initial natural diameter, and then one willproceed with the intervention (notably with mechanical cleaning) on thelatter.

The intervention may be made easier and more efficient if the bundle 3is expanded beyond its rated diameter, by this time applying excesspressure to it. During this operation care will be taken in order not todeform it beyond the elastic limit of the material used, so that it mayresume its rated diameter as soon cleaning and interruption of theexcess pressure has been completed.

In order to limit the deformation to a maximum controlled value of thebundle 3, the latter may be surrounded, as illustrated in FIG. 4, beforeapplying the excess pressure, by a ring or a sleeve, the inner diameterof which is equal to the maximum possible diameter which the bundle 3may assume without undergoing any deformation beyond its elastic limit.It is also possible to resort to rings 20, as illustrated in FIG. 5.

Once the intervention on the bundle is finished, a vacuum is againestablished in the latter so as to be able to easily place it in thecasing 1, and the vacuum pump is then disconnected so that the bundleresumes its rated dimensions and shape.

It is also possible according to the invention to resort to a change inrelative temperature in order to cause the bundle to contract or toexpand. Thus, before disassembling the bundle from its casing, astrongly cooled liquid notably close to or even less than 0° C. may becaused to flow in the bundle, so as to cause it to contract, and at thesame time the casing may be submitted to a higher temperature than roomtemperature so as to cause it to expand.

Of course, according to the invention, it is possible to have either thelow pressure and cooling, or the excess pressure and heating, act on thebundle simultaneously.

For certain applications, it is possible to provide the bundle 3 with adiameter less than the inner diameter of the casing 1. Such anarrangement is particularly interesting in that it provides automatic orquasi-automatic removal of brittle (limestone for example) depositswhich occur on the walls of the bundle. Indeed, it is sufficient tosubmit the bundle, for example during its operation, to an excesspressure (or a low pressure) of the fluid which flows through it inorder to deform and cause the bursting of the scale platelets whichcover it. These operations may even be performed automatically.

1-12. (canceled)
 13. A heat exchanger comprising two mutually isolatedfluid circuits in intimate thermal exchange contact, a first fluidcircuit, or bundle (3) being formed by a helical winding of two wallsand the second circuit being formed by an chamber containing the bundle(3), each circuit including its own fluid input and output means,characterized in that the bundle is elastically deformable under theeffect of excess pressure and low pressure.
 14. The exchanger accordingto claim 13, characterized in that said chamber is of a tubular shapeand when the internal pressure of the bundle is equal to externalpressure, its outer diameter is slightly less than or equal to the innerdiameter of the chamber.
 15. The exchanger according to claim 14,characterized in that the diameter difference between the inner face ofthe chamber and the outer face of the bundle is less than at most 6% ofthe diameter of the latter.
 16. The exchanger according to claim 13,characterized in that the tubular casing (1) includes two bottoms (19,25) at least one of which is removable and which are respectivelycrossed by fluid input (9) and output (11) means, and means capable ofproviding the seal between the bottoms and the fluid input and outputmeans of the bundle (3).
 17. The exchanger according to claim 16,characterized in that the means capable of providing the seal betweenthe tubes and the bottom consist of O-ring gaskets (23, 31) or astuffing box.
 18. A device for limiting an external diameter of a bundle(3) of an exchanger according to claim 13, characterized in that itconsists of least one calibrated component (20) the inner diameter ofwhich is equal to the maximum outer diameter which is intended to beadmissible and which is intended to be positioned around the latterafter having taken it out of the casing (1) in order to control thediameter thereof when it is submitted to excess pressure and/or to acontrolled rise in temperature.
 19. The device according to claim 18,characterized in that the aforesaid component consists of a ring orsheath (20).
 20. A method for intervening, such as notably for cleaning,on a bundle of a heat exchanger of the helical type including twomutually isolated fluid circuits in intimate thermal exchange contact, afirst fluid circuit being formed by a helical winding of two walls, orbundle, and the second circuit being formed by a space delimited by acasing containing the bundle, each circuit including its own fluid inputand output means, characterized in that it includes the steps of:submitting, before its removal, the bundle to low pressure and/orcooling relatively to its casing, so as to cause it to contract, settingback the bundle to pressure and/or room temperature once it has beenextracted from its casing, in order to cause it to recover its initialdimensions, proceeding with intervention on the bundle, again submittingthe bundle to low pressure and/or cooling relatively to its casing, inorder to cause it to contract before it is placed in the casing, settingback the bundle to pressure and/or room temperature once it has beenplaced back in its casing.
 21. The method according to claim 20,characterized in that it includes a preliminary step consisting ofdisconnecting the bundle from its circuit.
 22. The method according toclaim 20, characterized in that it includes an intermediate step beforethe step for intervening on the bundle, consisting of submitting thebundle to excess pressure and/or an increase in temperature relativelyto room temperature, in order to cause it to expand.
 23. The methodaccording to claim 22, characterized in that, before applying to thebundle (3) said excess pressure and/or said increase in temperature, adevice for limiting its diameter according to any claim 4 is positionedaround the latter.
 24. The method according to claim 20, characterizedin that it consists of producing the bundle (3) so that it is deformableunder the effect of a pressure difference between the bundle and thechamber, and of providing it with an outer diameter less than the innerdiameter of the casing (1) and of applying to the bundle periodicalexcess pressures and/or low pressures, in order to change its otherdiameter.